The present invention relates to driving circuit modules as unit devices, which have a main circuit including a plurality of power semiconductor elements connected in a bridge circuit, for driving inverters etc.
Power converting apparatuses such as inverters etc. are widely used for driving motors etc. Usually, the driving circuit devices for driving power converting apparatuses are constructed as three-phase or two-phase bridge circuits which comprise semiconductor power elements such as insulated gate bipolar transistors, bipolar transistors, field effect transistors, etc. In practice, it is quite convenient to unitarily incorporate the semiconductor power elements with related elements such as free wheeling diodes etc. into a module. The semiconductor elements as the module constituents may be individual elements mounted individually inside a package. However, it is far more effective for reducing size and cost of the driving circuit modules to mount as made constituent semiconductor element chips on a base of the module, and then, mount the base in a package case to form a whole driving circuit module.
The conventional driving circuit modules have a metal base plate made of Cu, for example, which has high thermal conductivity. Necessary numbers of electrode plates made of Cu, for example, are held on the metal base plate through insulator plate made of ceramic materials which have high thermal resistance. Chips of the constituent elements such as transistors, annexed diodes, etc., the constituents of the module, are mounted on and bonded with the electrode plates. Output and input terminals are connected with the electrode plates through conductors. The thus assembled driving circuit device is covered with or fitted to a molded resin case. A resin is injected into the space between the case and the base plate, and hardened to form a solid unitary module. As is well known, the driving circuit modules are used with their base plate fixed to an A1 radiator in tight thermal contact, and with their case mounted on an inverter etc.
It is necessary for using the driving circuit modules in various applications to incorporate a control circuit with the driving circuit module and to command detailed on-off operations to each semiconductor element constituting the bridge circuit corresponding to the application and the state of the load. Therefore, it has been required for simplifying the overall structure of the system including the control circuit to construct the driving circuit as an intelligent module which executes at least some functions which the control circuit does.
Since the control circuits may be electronic circuits which consume little electric power, the recent circuit integration techniques facilitate integrating the control circuits into a very small chip, though the control circuit may be complicated, and mounting the chip on a module. The most serious problem is that the control signal wiring is so complicated that it is necessary to lead out extra control signal lines for providing multi-purpose driving circuit modules.
The complexity of the wiring may be avoided by using wiring boards. But, the wiring board increases the size of the module to elongate the wiring length in the conventional module structures. The elongated wiring length increases the cost for compensating the wiring inductance by a capacitor or capacitors. Reduction of the space between the wiring conductors tends to cause mal-function by mutual interference of the control signals. Though the space may be reduced by using the base plate as the wiring board, it becomes very difficult to secure the withstand voltage between the high voltage power semiconductor elements and the control circuit.